Yield, Nitrogen Uptake and Nitrogen Leaching of Sensor-Based Fertigation-Cultured Tomato in a Shallow Groundwater Region: Effect of Shallow Groundwater on Tomato Irrigation

Fertigation with surface drip has been introduced and broadly applied for vegetable cultivation in the Eastern China, which presents high precipitation and always has shallow groundwater. To estimate the influence of high groundwater level on the tomato nitrogen (N) and water use efficiency and develop new sensor-based fertigation technology, experiments were executed in plastic greenhouse in the experimental farm of Yangzhou University located in the suburban of Yangzhou city during 2016-2017 growing seasons using a block randomization with three replications. Three N dosages and 4 watering treatments were carried out in this experiment. The data indicated that irrigation threshold of -35 kPa was optimum to get the maximum production of tomato. In this treatment, the value of estimated plant evapotranspiration (ETc) was much higher than total applied water volume, suggesting high groundwater table had a significant contribution on the tomato ETc and a sensor-based irrigation strategy should be more accurate than the simulated ETc irrigation method to calculate the water demand under this condition. In addition, our results indicated that high groundwater level had a positive effect to alleviating N leaching. Finally, we can conclude that fertigation technology enhanced the N use efficiency (NUE) and water use efficiency (WUE) and three fourths of the calculated N dosage (according to a traditional nutrient equation) was sufficient to optimize tomato yield.